98 MERCURY SABLE. SPEEDOMETER STOPPED WORKING AND THEN THE TRANSMISSION WOULD NOT SHIFT PROPERLY. IT REVS HIGH AND THEN WHEN YOU LET UP ON THE GAS IT WILL SHIFT. I WAS TOLD IT IS THE OUTPUT SPEED CENSOR, HOWEVER I DO KNOW WHERE IT IS AND IF THIS IS THE PROBLEM. THANKS

VSS - vehicle speed sensor maybe . Does the transmission shift properly ?

speed sensor failure

Symptoms of a P0500 DTC may include
: loss of anti-lock brakes the "anti-lock" or "brake" warning lamps on the dash may be lit the speedometer or odometer may not work properly (or at all) your vehicle's RPM limiter may be decreased the shifting of an automatic transmission may become erratic other symptoms may also be present

Read more at: https://www.obd-codes.com/p0500
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If the speedometer stops working the odometer stops also. Sounds like it is stuck in first gear. The RPM went up because the throttle was response to pedal but transmission not response. Check transmission fluid color. Whip off dipstick on a white paper towel look for gray if see any that is metal shavings and transmission is bad.

A sensor inside steering column is malfunctioning

Yes

Hello wsarah03,

There is a Vehicle Speed Sensor (VSS) mounted on the transaxle, that is a good place to start. The VSS tells the powertrain management system when and how to shift the transmission and also gives the speedometer it's signal.

From your description that the speedometer quit working at the same time I would suspect the a faulty VSS.

Regards,
netvan

VSS (vehicle speed sensor) Tells the PCM (computer) the speed of the vehicle so the PCM can make the proper information to the TCM (transmission control module) to shift.
YOU are goin gto need a scan tool NOt a code reader to monitor the VSS to see what it is putting out for speed when the car is moving But I believe you need a VSS but do not not Go out and buy one until you have had it tested , and can positively confrim it is bad first. Please rate this a fixya if you find this advice helpful, Thanks Randy

Check your transmission fluid. You could be alittle low. Check it hot in Park while running.

Check the transmission fluid first. it sounds like one of the clutch plates is sticking.

If you shift into second after you've stopped, can you get the car moving?

I hace a 19196 sable-the problem is the transaxle speed sensor-this part sends all speed info to the computer ..-First symptom(speedometer stops working and then transmission shifts erratacially and power steering becomes hard and engine light comes on..The computer on this all eletronic car cannot send proper signals to the speedo-trans-power steering and other functions without knowing how fast or slow the car is going..Have the SPEED SENSOR mounted on top of the tranaxle replaced and all will be well.Part is not to expensive.labor can vary depending whether you have 3.0OHV or DOHC engine-some cars have to have exhaust dropped to get at it-Good Luck All